The invention relates to a paper feeding apparatus, and more particularly, to such apparatus capable of feeding both manually loaded papers and papers contained in a cassette.
A cassette feeder system is known as one of feeders utilized in the art of copying machines. This permits a series of sheets, cut to size, to be fed in succession, and provides copies of a given size, which is convenient for editing and binding purposes. A plurality of cassettes are provided in accordance with different sizes of the sheets, and are selectively loaded into the machine in accordance with the size of an original.
Considering some situations which occur when using a copying machine which is provided with a cassette feeder, it may be desired to obtain a copy of A4-size (210 mm.times.297 mm). If the cassette loaded into the machine is of the same size, there is no problem. However, if the paper size of the loaded cassette is different, it is necessary to change the cassette even though a single copy is desired. Also, it may sometimes be desired to obtain a single copy from a different original in the course of a succession of copying operations. If the cassette loaded is the same size as that for the desired copy, it is possible to interrupt the succession in order to obtain the single copy. However, if the paper size of the loaded cassette is different, the desired copy must be obtained by changing the cassette after the succession of copying operations have been completed, thus requiring a waste, waiting time.
To overcome the above difficulties, there is also provided a so-called multiple feeder mechanism which is provided with a plurality of cassettes of different paper sizes and which selectively supplies one of them. However, the use of such multiple feeder mechanism results in an increased overall dimension of the copying machine. Furthermore, the mutiple mechanism generally includes only two different sheet sizes, and if the loaded cassette is of a size which is different from that for a desired copy, the cassette must be changed even though the number of desired copies is only one.
The change of the cassette can be avoided by providing a paper feeding apparatus which includes a manually loaded paper feeder in addition to the cassette feeder so that a desired copy or copies can be obtained by utilizing the manual feeder mode. However, conventional paper feeding apparatus of this kind includes a cassette and a manually loaded paper feeder which operate independently from each other, resulting in a complex and bulky arrangement.
One form of paper feeding apparatus includes a feed roller which is disposed at a fixed position and below which a sheet cassette carrying a plurality of sheets is disposed. A baseplate in the cassette may be moved upwardly to bring an uppermost sheet into abutment against the roller in order to deliver that sheet. In the conventional arrangement, the baseplate is raised or lowered by a pusher member disposed in a cassette receiving portion of the copying machine, for example, and which is movable in the vertical direction to engage with or disengage from the baseplate, the pusher member being operated by an operating member which projects out of the copying machine. The sheet cassette cannot be removed unless the operating member has released the pusher member. However, in a paper feeding apparatus which is selectively capable of a cassette feeder operation employing the vertical movement of the bottom plate and of the feeding of a manually loaded paper, an inadvertent rise of the baseplate may result in feeding a sheet from the cassette when the feeding of manually loaded paper is desired. Additionally, an accidental rise of the pusher member or lever when the cassette is not loaded may result in the engagement of the lever with the feed roller, which is undesirable.
In a system employing the cassette feeder, a paper detector is usually disposed adjacent the loading position of the cassette in order to detect the presence or absence of a sheet or sheets in a cassette to disable each copying unit including the paper feeder if the absence of sheet is detected even though the cassette is properly loaded in position. The detector also disables the copying operation whenever the cassette is not properly loaded. A control of the copying operation in response to such detection is satisfactory in a paper feeding apparatus which is only capable of a cassette feeder operation. However, in a paper feeding apparatus which is designed to provide the feeding of a manually loaded paper as well, the detection of the presence or absence is insufficient, and it is also necessary to check the position or orientation of the manually loaded paper.